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We report a case of HeartWare ventricular assist device (HVAD) implant as a Bridge-to-Transplant in the smallest and the youngest known patient, a 32-month-old boy (body surface area of 0.66 m2) with known Kawasaki disease and giant coronary artery aneurysms. The disease course was complicated by coronary thromboembolism resulting in acute myocardial infarction, ventricular fibrillation, and cardiac arrest. After short-term support with extracorporeal membrane oxygenation for 7 days and long-term support with an HVAD for 5 months, he underwent heart transplantation and is doing well 2 months after the transplant.

From the *Division of Cardiothoracic Surgery, Cardiac Center, The Children’s Hospital of Philadelphia, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania

†Division of Cardiology, the Children’s Hospital of Philadelphia, Perelman School of Medicine and the University of Pennsylvania, Philadelphia, Pennsylvania.

Submitted for consideration December 2016; accepted for publication in revised form March 2017.

Case Report

A 32-month-old boy (height, 99 cm; weight, 16 kg) was admitted with Kawasaki disease (KD) and an outside echocardiogram finding of giant coronary artery aneurysms involving the proximal left anterior descending (LAD) and the proximal right coronary artery (RCA). His admission echocardiogram showed a large aneurysm in the proximal RCA measuring 1.5 × 1.5 cm and an aneurysm in the proximal LAD measuring 1.9 × 2.6 cm, containing a large thrombus, along with mild dilation and mildly diminished left ventricular (LV) systolic shortening (ejection fraction of 45%, shortening fraction of 25%), normal LV free wall motion, dyskinetic ventricular septal motion, and normal right ventricular (RV) size and function. His electrocardiogram was notable for T wave inversions in leads aVL and V1–V4 without ST (the ST segment is the flat, iso electric section of the ECG between the end of the S wave (the J point) and the beginning of the T wave) segment depression. Heparin infusion was started immediately and thrombolysis with systemic tissue plasminogen activator was performed. Cardiac catheterization (Figure 1) after thrombolysis showed decreased clot burden in the coronary aneurysm and heparin was continued. However, an echocardiogram 2 days later showed moderately diminished LV function with an ejection fraction of 40% with severe hypokinesis of the anterior wall and anteroseptal portion of the LV with reappearance of thrombus in the LAD aneurysm, which measured 2 cm. Contrast-enhanced magnetic resonance imaging (Figure 2) was done, which confirmed the echocardiogram findings. Thrombolysis was repeated after which he had an episode of bradycardia with ST segment elevation. He rapidly developed hypotension during this episode, which progressed to ventricular fibrillation and cardiac arrest. Emergency cannulation for veno-arterial extracorporeal membrane oxygenation (ECMO) was performed through the right carotid artery and right internal jugular vein. Postevent echocardiogram showed very poor biventricular function and elevated troponin levels suggesting an ischemic event. Extracorporeal membrane oxygenation flows were maintained at 90–100 ml/kg/min and activated clotting time in the range of 200–220 seconds.

After a week of uncomplicated ECMO support and after confirming normal neurological and end organ function and acceptable RV function (mildly diminished RV systolic shortening), it was decided to implant a HeartWare left ventricular assist device (HVAD; HeartWare Inc., Framingham, MA) for long-term mechanical circulatory support. Considering the small size of the patient (body surface area (BSA) of 0.66 m2), the bilateral pleural spaces were opened and the pericardium was incised posteriorly along the diaphragmatic surface with care taken to preserve the phrenic nerves (Figure 3). After cannulating the aorta and the vena cavae and placing a left atrial vent, the HVAD was implanted in the LV apex using four spacer rings cut out from felt to prevent the mitral valve leaflets from obstructing the tip of the inflow cannula. The rest of the procedure was similar to standard HVAD implantation. He was weaned off cardiopulmonary bypass on inotropic support of epinephrine, 0.05 mcg/kg/min; milrinone, 0.6 mcg/kg/min; dopamine, 5 mcg/kg/min; and isoproterenol at 0.01 mcg/kg/min and inhaled nitric oxide at 40 parts per million. Heparin infusion was started on postoperative day 1 with a goal partial thromboplastin time of 50–60 seconds and anti-Xa level of 0.3–0.7 IU/ml. The initial HVAD settings were as follows: 2,000 revolutions per minute (RPM), which resulted in a cardiac output of 1.9 liters per minute (lpm) and power of 1.6 watt. The systemic blood pressure was in the range of 70–80 mm Hg and the right atrial pressure ranged from 8 to 12 mm Hg, no left atrial (LA) line was inserted and LA pressure was not monitored. Postoperative echocardiogram showed good decompression of the LV and moderate-to-severe RV dysfunction. The RPMs and flows were adjusted to keep the septum in midline and prevent it from bowing into the LV. There was no inflow cannula obstruction by the mitral valve leaflets (Figure 4) and no opening of the aortic valve. Occasional low flow alarms were managed by fluid replacement.

On postoperative day 2, there were concerns about RV failure heralded by elevated right atrial pressure in the range of 16–18 mm Hg and hepatomegaly. The patient responded well to diuretics and flows gradually increased to 2.5 lpm on the same settings. With gradual diuresis, stable HVAD flows and organ function, the patient was extubated on postoperative day 7 and sildenafil and aspirin were started. On postoperative day 9, lactate dehydrogenase (LDH) enzyme levels were elevated to 2,200 U/L. Attributing the rise in LDH to hemolysis, the RPM were decreased to 1,900 and the LDH trended down to < 1,000 U/L. Inotropic support and inhaled nitric oxide were discontinued by postoperative day 10 and he was listed for heart transplantation. Coumadin was started and the patient was transferred to the step-down unit where his international normalized ratio (INR) was maintained between 2 and 2.5. During his postoperative course, there were no further episodes of thromboembolism in the coronary aneurysms as suggested by ECG changes or by worsening of RV function.

After 5 months of HVAD support, a suitable donor became available and the boy underwent cardiac transplantation. Dense adhesions were noted during the HVAD explant especially near the left lung and the phrenic nerve pedicle. The procedure was complicated by left hemi-diaphragm paralysis for which he underwent diaphragm plication. The rest of the posttransplant course was uneventful and he was discharged on postoperative day 10 after catheterization revealed reassuring hemodynamics and a biopsy showing grade 1R rejection.

Comment

Cardiac transplantation is a feasible option in patients with Kawasaki disease with extensive or distal coronary involvement and in those with disease course complicated by coronary thromboembolism, resulting in severe irreversible myocardial dysfunction secondary to infarction.1 Hemodynamically unstable patients require mechanical circulatory support to stabilize them and bridge them to heart transplant. Numerous such devices exist in the adult population but there is a scarcity of smaller pediatric-specific devices. Some devices that were designed primarily for adults have been successfully used in children older than 11 years of age and with body surface area greater than 1.2 m2. However, there is concern that the low stroke volume that must be used in children results in inadequate pump washout and an excessive thromboembolic risk.2

Mechanical circulatory support in complicated KD awaiting heart transplant with both LV as well as biventricular support has been described with the use of Berlin heart.3 Although the use of Berlin Heart EXCOR has improved survival in this patient population, there is a high incidence of bleeding, infection, and neurological dysfunction.4 Of note, our patient’s postoperative course was not complicated by any neurological event or any anticoagulation-related complication. Modification of HVAD implantation technique with the use of spacer rings has been described before by Hetzer et al. who used these spacer rings while implanting the HVAD in the systemic right ventricle in a patient with hypoplastic left heart syndrome to keep the inflow tip away from the tricuspid valve leaflets.5 We adopted a similar technique in our patient as the left ventricle was not severely dilated, to keep the mitral leaflets away from the inflow cannula and to prevent them from getting sucked into the HVAD inflow. There were no suction events and stable flows were maintained throughout the postoperative period.

To our knowledge, this is the smallest (BSA, 0.66 m2) and the youngest (age, 32 months) case report of successful HVAD implant as a bridge to transplant. There are studies describing successful outcomes after HVAD implant in children5 and adolescents6 but none of them include a patient as small and as young as in this case report. Also, it is the first reported successful and uncomplicated use of an HVAD in a patient with complicated Kawasaki disease.